Subject: RE: AES draft...

From: "Paul Leach" <[email-masked]>
Date: Mon, 5 May 2003 13:03:13 -0700

It's really a description, not a definition.

It was based on the following: in my simple timing model, I said:

"A reasonable password cracking dictionary might have 2**21 entries;
complexity rules forcing mixed case, digits and punctuation could
plausibly add 2**11 combinations for each dictionary word, resulting in
2**32 possibilities."

Experience says that users won't like even being forced to do that much.
It leads to passwords that are too long.

I'll grant that one could _generate_ passwords with more entropy than that
that were still memorable, but I don't think that more than a small
fraction of users would ever choose such passwords voluntarily, and they
would still be too long for most user's taste.

> -----Original Message-----
> From: Ken Hornstein [mailto:[email-masked]] 
> Sent: Monday, May 05, 2003 11:00 AM
> To: [email-masked]
> Subject: Re: AES draft... 
> 
> >Also, if this WG would not be so embarassed that it 
> prominently put in 
> >the draft that with a recommended default of 1 any person 
> with one 2ghz 
> >PC could crack in 6 hours the most complex password a normal 
> user would 
> >believably use, then I won't even object, although I'd prefer not to 
> >call that a "recommendation".
> 
> I think I missed something ... what is your definition of 
> "the most complex password a normal user would believably use"?
> 
> --Ken
> 
> 
> 
>

---

From: Ken Hornstein <[email-masked]>
Date: Mon, 05 May 2003 16:49:48 -0400

>plausibly add 2**11 combinations for each dictionary word, resulting in

Alright, now I've got a handle on what we're talking about here.

I just checked my password database on our KDC; we use a dictionary which
has a little more than 2**20 entries.  We're using a cracklib-based password
quality checker based on code from Matt Crawford; this catches the obvious
"add a number to the end of a dictionary word" kinds of things, and all of
the obvious mixed case stuff.  So I'm reasonably confident that it would
take longer than six hours to break our average password with common
hardware today.

>It leads to passwords that are too long.

Well, we've been doing this for a couple of years, and while it's not
popular, it seems to be liveable.  People tell me they come up with uncommon
acronyms, pass phrases, first letter of each word in a sentence, etc etc.
It's certainly liveable.

I think the guidance you proposed in your other email is fine.

--Ken